1. Field of the Invention
This invention pertains generally to imaging and more particularly to ultrasound imaging.
2. Description of Related Art
Time-reversal (TR) methods have received considerable interest in many areas, with applications ranging from the destruction of kidney stones, to the detection of flaws in solids, and to ultrasound medical imaging. One of these methods is the Time-Reversal with Multiple Signal Classification (TR-MUSIC) imaging algorithm developed by Devaney. This algorithm combines TR focusing with the MUSIC signal-subspace algorithm.
Numerical and experimental studies that used the MUSIC algorithm with TR imaging showed that when the targets are much smaller than the ultrasound wavelength, images with sub-wavelength resolution can be achieved. The high-resolution capability of TR-MUSIC imaging may find many applications in medical ultrasound. One area of interest is the detection of breast micro-calcifications, which are the first sign of breast cancer for more than half of all breast cancer cases.
The TR-MUSIC algorithm assumes that the ultrasound attenuation of the medium is negligible, and does not account for the finite-size effects of the transducer elements. In addition, the algorithm is applicable only when the number of point scatterers is fewer than the number of elements in a transducer array.
Accordingly, an object of the present invention is a generalized TR-Music method to account for ultrasound tissue attenuation and the finite-size effects of transducer elements. Another object is a windowed TR-MUSIC method for imaging point scatterers when their number exceeds the number of ultrasound transducers in the scanner array, or imaging extended targets. At least some of these objectives will be met in the description below.